Journal Article

The chemical evolution of globular clusters – I. Reactive elements and non-metals

A. Marcolini, B. K. Gibson, A. I. Karakas and P. Sánchez-Blázquez

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 395, issue 2, pages 719-735
Published in print May 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14591.x
The chemical evolution of globular clusters – I. Reactive elements and non-metals

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We propose a new chemical evolution model aimed at explaining the chemical properties of globular clusters (GCs) stars. Our model depends upon the existence of (i) a peculiar pre-enrichment phase in the GC's parent galaxy associated with very low-metallicity Type II supernovae (SNe II) and (ii) localized inhomogeneous enrichment from a single Type Ia supernova (SN Ia) and intermediate-mass (4–7 M) asymptotic giant branch field stars. GC formation is then assumed to take place within this chemically peculiar region. Thus, in our model the first low-mass GC stars to form are those with peculiar abundances (i.e. O-depleted and Na-enhanced), while ‘normal’ stars (i.e. O-rich and Na-depleted) are formed in a second stage when self-pollution from SNe II occurs and the peculiar pollution from the previous phase is dispersed. In this study, we focus on three different GCs: NGC 6752, 6205 (M 13) and 2808. We demonstrate that, within this framework, a model can be constructed which is consistent with (i) the elemental abundance anticorrelations, (ii) isotopic abundance patterns and (iii) the extreme [O/Fe] values observed in NGC 2808 and M 13, without violating the global constraints of approximately unimodal [Fe/H] and C+N+O.

Keywords: nuclear reactions, nucleosynthesis, abundances; stars: abundances; stars: AGB and post-AGB; stars: chemically peculiar; globular clusters: individual: NGC 6752, NGC 6205, NGC 2808

Journal Article.  14505 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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